Process of producing tetra alkyl lead



Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE PROCESS OF PRODUCING TETRA ALKYL LEAD No Drawing. Application March 28, 1931,

1 Serial No. 526,127

20 Claims.

This invention relates to the process of manufacturing tetra alkyl lead, and more particularly to the process of controlling the reaction between large amounts of lead'mono-sodium alloy and alkyl chloride, and especially ethyl chloride.

It has been known thatsmall amounts of lead mono-sodium alloy can be mixed with varying excessive amounts of ethyl chloride, and the mixture sealed in small autoclaves or bombs and heated to temperatures under 125 C. by means of a water or oil bath or the like, and that when the mixture was subjected to such treatment no adverse pressure or temperature phenomena developed.

It has, however, never been possible to subject relatively large amounts of the lead alloys and ethyl chloride to this treatment because of the fact that when as much as three or more pounds of the alloy are treated with ethyl chloride sufficient to cause reaction, the coolingsurface is apparently no longer suflicient to conductaway the heat, liberated by the highly exothermic reaction which takes place and as a result explosion occurs. Y i

An object of the present invention is to overcome the disadvantages heretofore described and to improve generally on the process of producing tetra alkyl lead, and particularly tetra ethyl lead.

These objects are accomplished by the following invention in which we have found that good found, furthermore, particularly in the case of tetra ethyl lead, that a satisfactory reaction can be brought about provided a relatively small proportion of the total amount of ethyl chloride to be used is added to the alloy which has been previously charged into an agitated and water-jacketed autoclave, and allowed to react. According to our present invention the alloy is first warmed to approximately to 50 C. by circulating warm water (e. g., to C.) and the small amount of ethyl chloride added. This small amount of ethyl chloride is allowed to react until indication of reaction is apparent by a drop of pressure against a rising temperature. This preliminary reaction, we have found, prepares the surface of the alloy and renders it capable of reacting with they remaining necessary quantity. of ethyl chloride as rapidly as it is added. A particularly important feature of this reaction carried out in this way is that dangerous accumulations of ethylchloride is avoided. 'When the reaction is thus started it is possible to control the rate of ethyl chloride addition so that heat is liberated no faster than it can be removed. When the initial increment of ethyl chloride has reacted the circulation of warm water is stopped and the circulation of cool water (e. g.,,l to 25 C.) is started. It is nowpossible to proceed with the addition of 'the remaining ethyl chloride at a fairly rapid rate, which permits the addition of the complete amount of ethyl chloride in one and one-half to two hours. When all of the ethyl chloride has been added the charge is cooled until the, pressure has fallen back a reasonable amount (e. g., 2 to 50 lbs), after which time the reaction is completed by circulating warm Water (35 to C.) in the jacketfor from one and one-half to five and one-half hours.

If desired, the ethyl chloride need not be added in one continuous addition, but the addition may be interrupted when approximately one-half of the ethylchloride has been added and the pressure within the vessel has been reduced a reasonable amount (e. g., 2 to 50 lbs.) by cooling. When this has occurred the balance of the ethyl chloride may be added. We have found it essential that the ethyl chloride be added as quickly as possible after the preliminary reaction has once taken place. The following example is given as illustrative of one specific embodiment of our invention, but it is to be understood that this is not to be considered in any way as limiting the invention:

' Example Twenty-five hundred pounds of lead monosodium alloy are charged into a suitable agitated, water-jacketed autoclave. The alloy is heated by the circulation of warm (35 to 55 C.) water in the jacket until a temperature of 35 to 50 C. is attained. When this temperature is reached, 25 to 50 pounds of ethyl chloride are added. The pressure will rise 10 to 40 pounds. Warm water is circulated in the jacket of the autoclave and the temperature will continue to rise. After approximately 15 minutes the pressure will start to fall. The fall of pressure when accompanied by rising temperatures shows clearly that reaction between lead mono-sodium alloy and ethyl chloride hasoccurred and that the ethyl chloride which was added is being absorbed." This is assurance that further addition of ethyl chloride may safely be made. When the pressure has fallen 2 to 8 pounds against a rising temperature the addition of ethyl chloride is resumed and continued at such a rate that approximately one-half of the total of from 800 to 1,000 pounds is added in 15 to 30 minutes. Cooling'with cool water (1 to 25 C.) is started when the addition of ethyl chloride is resumed.

When the first half of the ethyl chloride has been added, the pressure is reduced by the continued circulation of cold water until it has fallen 10 to pounds. After the pressure has fallen the addition of ethyl chloride is resumed, and

the balance of the 800 to 1,000 pounds is added in 15 to 30 minutes. Slightly longer time ,may be consumed for the addition of ethyl chloride but without advantage.

When all of the ethyl chloride has been added, the charge is cooled by the continued circulation of cold water ('1 to 25' C.) in the jacket until the pressure has fallen 10 to 50 pounds. When the pressure has fallen the circulation of cool water is discontinued and the reaction is completed by the circulation of warm (35 to C.) water in the jacket for a period of time varying between one and one-half hours to five and onehalf hours.

While our invention has been specifically illustrated as ap lied to the production of tetra ethyl lead, it will be apparent that this process may also be applied to the production of other tetra alkyl lead compounds, and particularly tetra methyl lead 'tetra propyl lead, and the like.

As many apparently widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that we 'do not limit ourselves to the foregoing examples or descriptions except as indicated in the following patent claims:

We claim:

1. In the process of making tetra alkyl lead by the reaction of alkyl chloride and lead monosodium alloy, the step which comprises first reacting with the alloy a small increment of the theoretical amount of the alkyl chloride required for complete reaction with the alloy present, and then adding to the alloy the required amount of alkyl'chloride for completereaction.

2. In the process of making tetra alkyl lead by the reaction of alkyl chloride and lead monosodium alloy, efiecting a reaction on theisurface of the alloy with less than the-theoretical amount of alkyl chloride required for complete reaction with the alloy, and subsequently adding to the alloy the required amount of alkyl chloride for complete reaction.

3.'In the process of:making tetra alkyl lead by the reaction of alkyl chloride and lead monosodium alloy, which comprises adding to the alloy a small increment of the theoretical amount of alkyl chloride required for complete reaction with the alloy present, allowingthe reaction to proceed until the pressure drops against a rising temperature, and then adding the required amount of alkyl chloride for complete reaction.

4. In the process of making tetra ethyl lead by the reaction of ethyl chloride and lead monosodium alloy, the step which comprises first reacting with the alloy a small increment of the theoretical amount of the ethyl chloride required for complete reaction with the alloy present, and. then adding to the alloy the required amount of ethyl chloride for complete reaction.

5. The process of claim 4 in which the temperature of the alloy is raisedtoapproximately 25 to 50 C. before the small increment of ethyl chloride is added. 1

6. The process of claim 4 in which the required amount of ethyl chloride is added ata rate which permits the heat to be removed as rapidly as it is formed.

7. In the process of making tetra ethyl lead by the reaction of ethyl chloride and lead monosodium'alloy, efiecting a reaction on the surface of the alloy with less than the theoretical amount of ethyl chloride required for complete reaction with the alloy, and subsequently adding to the alloy the required amount of ethyl chloride for complete reaction, 1

8. In the process of making tetra ethyl lead by the reaction of ethyl chloride and lead monosodium alloy, which comprises adding to the alloy 9. small increment of the theoretical amount of ethyl chloride required for complete reaction with the alloy present, allowing the reaction to proceed until the pressure drops against a rising temperature, and then adding the required amount of ethyl chloride for complete reaction.

9. The process of claim 8 in which the temperature of the alloy is raised to approximately 25 to 50 C. before the small increment of ethyl chloride is added.

10. The process of claim 8 in which the required amount of ethyl chloride is added at a rate which permits the heat to be removed. as rapidly as it is formed.

11. The process of claim 8 in which the pressure drop is about 2 to about 50 pounds.

12. In the process of making tetra ethyl lead by the reaction of ethyl chloride and lead monosodium alloy in an autoclave, the steps which comprise raising the temperature of the alloy to approximately 25 to 50 0., effecting a reaction between the alloy and a small increment of the theoretical amount of the ethyl chloride required" reacting with the alloy approximately one-half of the required amount of alkyl chloride for complete reaction, cooling the reaction mass andreducing the pressure, and then adding the remaining quantity of alkyl chloride required for the complete reaction.

the reaction of alkyl chloride and lead monosodium alloy, the steps which comprise first reacting with the alloy a small incrementof the theoretical amount of the alkyl chloride required for complete reaction with the alloy present, then reacting with the alloy approximately one-half the required amount of alkyl chloride for complete reaction, reducing the pressure about 10 to about 50 pounds bycooling, and then adding the remaining quantity of alkyl chloride required for complete reaction.

15. In the process of making tetra alkyl lead by the reaction of alkyl chloride and. lead monosodium alloy, the steps which comprise adding to the alloy a small increment of the theoretical amount of alkyl chloride required for complete reaction with the alloy present, allowing the reaction to proceed until the pressure drops against a rising temperature, then adding approximately o-ne-halfaof the required amount of alkylchloride:

5.0 14. In the process of making tetra alkyl lead by i 16. In the process of making tetra, ethyl lead by the reaction of ethyl chloride and lead monosodium alloy, the steps which comprise first reacting with the alloy a small increment of the theoretical amount of the ethyl chloride required for complete reaction with the alloy present, then reacting with the alloy approximately one-half of the required amount of ethyl chloride for complete reaction, cooling the reaction mass and reducing the pressure, and then adding the remaining quantity of the required amount of ethyl chloride for complete reaction.

1'7. In the process of making tetra ethyl lead by the reaction of ethyl chloride and lead monosodium alloy, the steps which comprise efiecting a reaction on the surface of the alloy with less than the theoretical amount of ethyl chloride required for complete reaction with the alloy, subsequently reacting with the alloy approximately one-half of the required amount of ethyl chloride for complete reaction, reducing the pressure about to about 50 pounds by cooling and then adding the remaining quantity of the required amount of ethyl chloride for complete reaction.

18. In the process of making tetra ethyl lead by the reaction of ethyl chloride and lead monosodium alloy in an autoclave, the steps which comprise raising the temperature of the alloy to approximately 25 to 50 C., effecting a reaction between the alloy and a small increment of the theoretical amount of the ethyl chloride required for complete reaction with the alloy, lowering the pressure by cooling with water, then reacting the alloy with approximately one-half of the required amount of ethyl chloride for complete reaction, reducing the pressure about 2 to about 50 pounds by cooling, and then adding the remaining quantity of the required amount of ethyl chloride for complete reaction.

19. In the process of making tetra alkyl lead by the reaction of alkyl chloride and lead monosodium alloy, the steps which comprise adding to the alloy a small increment of the theoretical amount of alkyl chloride required for the complete reaction with the alloy present, allowing the reaction to proceed until the pressure drops against a rising temperature before adding further amounts of the alkyl chloride, and then, when the pressure has dropped about 10 to about 50 pounds, at once commencing the addition of the required amount of alkyl chloride for complete reaction.

20. In the process of making tetra alkyl lead by the reaction of alkyl chloride and lead monosodium alloy, the steps which comprise adding to the alloy a small increment of the theoretical amount of alkyl chloride required for complete reaction with the alloy present, allowing the reaction to proceed until the pressure drops against a rising temperature before adding further amounts of alkyl chloride and then, when the pressure has dropped about 10 to about 50 pounds, at once commencing the addition of the required amount of alkyl chloride for complete reaction at such a rate that the heat formed during the reaction will be removed as rapidly as it is formed.

WILLIAM S. CALCOTT. ALFRED E. PARMELEE. JOSEPH L. STECHER. 

